The present disclosure relates to non-aqueous electrolyte cells and positive electrodes for non-aqueous electrolyte cells. Specifically, the present disclosure relates to a positive electrode for a nonaqueous electrolyte cell, the positive electrode including a coating containing a compound for which a peak in a phosphorus 2p spectrum obtained by X-ray photoelectron spectroscopy is within a predetermined region, and a nonaqueous electrolyte cell including the positive electrode.
In recent years, portable electronic devices, such as camcorders, video cameras, digital still cameras, cellular phones, personal digital assistants, and notebook computers, each achieving a reduction in size and weight have appeared one after another. Cells, in particular, secondary cells have been receiving attention as portable power supplies for such electronic devices. Intensive studies have been conducted to develop secondary cells with a higher energy density. As secondary cells having a high-energy density, lithium-ion secondary cells have been developed and are now in practical use.
Hitherto, in lithium-ion secondary cells, nonaqueous electrolytic solutions containing lithium salts dissolved in non-aqueous solvents have been used as ionic conductors. To prevent leakage of electrolytic solutions, metal cases need to be used as housings to reliably secure the hermeticity of cells.
However, when metal cases are used as housings, it is significantly difficult to make large-area thin sheet cells, small-area thin card cells, and flexible cells.
In place of electrolytic solutions, Japanese Unexamined Patent Application Publication No. 2001-283910 discloses a secondary cell including a nonaqueous gel electrolyte for which an electrolytic solution is retained in a polymer. In this secondary cell, there is no leakage of electrolytic solutions. Thus, a housing may be formed of, for example, a laminate film, thereby achieving a further reduction in size, weight, and thickness and achieving higher flexibility.
However, when housings are formed of laminate films and the like, cells may expand with gases generated by decomposition of electrolytic solutions during high-temperature storage. Therefore, there is still room for improvement.
It is desirable to provide a positive electrode for a nonaqueous electrolyte cell, the positive electrode being capable of inhibiting or preventing the cell from expanding, and a nonaqueous electrolyte cell including the positive electrode.